Composting organic matter is a great way to reuse the nutrients. You will be setting up an experiment that tests to see the effectiveness of composting after one week and one month.
Find organic waste (food scraps, excluding animal byproducts) to collect. Look up ways to improve your compost by hastening decomposition. Include this in your experimental procedures. Create a “control” group of compost by including the same organic waste, but without any of the methods of hastening decomposition. Make hypotheses about how much will decompose and after how long. Find a place for your compost and set a date for retrieval.